Fisheye Lenses

A fisheye lens is an ultra-wide-angle lens with an angle of view of 180 degrees or more. The design and shape of these lenses bear resemblance to the eyes of fish, hence the name. These optical systems inherently produce perspective distortion that cannot be corrected, resulting in a peculiarly distorted convex-rounded image, which is the defining characteristic of fisheye lenses.

In practice, there are two primary types of fisheye lenses:

1. Circular lenses: These lenses produce a circular image within the film frame, providing a 180-degree angle of view in all directions.
2. Diagonal or full-frame lenses: The image circle of these lenses surrounds the film, resulting in a 180-degree angle of view only along the diagonal of the frame.